The present invention relates to archery products, and more particularly to an axle assembly for a cam on an archery bow.
Conventional compound and crossbow archery bows include a bowstring and a set of power cables that transfer energy from the limbs and cams, eccentrics or pulleys (which are all referred to generally as “cams” herein) of the bow to the bowstring, and thus to an arrow shot from the bow. The function of the cams is to provide a mechanical advantage so that energy imparted to the arrow is a multiple of that required of an archer to draw the bow. The cams typically are rotatably mounted to limbs via respective axles.
Generally, there are two primary types of limb systems for archery bows. Some bows include solid limbs that define recesses configured to receive cams near the free ends of the solid limbs. The remainder of the solid limbs, from the recess to the riser, is solid and one piece. Other bows include split limbs, which include two parallel, smaller limbs that are generally separate from one another along their length from the cam to the riser. Each type of limb system offers certain advantages over the other, while each also has its drawbacks.
One drawback of split limb systems, (and even some solid limb systems) is that most have a floating axle system that takes up some, but not all of the slop and spacing between different components mounted between the ends of the axle. Typically, a floating axle system includes a predetermined overall stack up width (the width of cam components “stacked” adjacent one another on the axle) defined by the two e-clips registered in corresponding grooves on the axle. These systems typically include multiple flat spacers or washers of random thickness to establish the predetermined overall stack up width. The spacers are helpful in that they can locate the cam components in a general lateral position relative to one another, however, with this floating axle system, it is virtually impossible to eliminate all the gaps between cam components on the axle without compressing and binding bearings disposed along the axle that assist in rotation of the cams. Thus, virtually all of these floating axle systems have gaps between the components on the axle. Accordingly, the cams and components can slide laterally along the axle, which can lead to inconsistent and/or imprecise rotation of the cams.
Some manufacturers have attempted to replace floating axle systems with threaded axle systems that delete the e-clips. In a threaded axle system, an axle is provided with a threaded opening at one or both ends, and a corresponding fastener is threaded into the opening in an attempt to eliminate excess space between components along the axle, such as bearing, cams and bushings. While some claim that this threaded axle system provides zero tolerance and zero space between the components, it is believed that in reality, there is some space between the elements, especially when the components wear at the points of contact over time. This can lead to larger unwanted gaps and lateral movement along the axle, which again generates inconsistent and sometimes slightly misaligned rotation of the components on the axle. Further, these systems are designed so that the tightening of the fastener does not compress the components along the axle (the components are merely very close to one another), which compression can crush the bearings such that the cam will not rotate well in this system. In most cases, these systems are designed so the fastener bottoms out before putting any compression on the components along the axle, which again results in those systems failing to eliminate all the slack and gaps in the stack up of components along the axle.
Accordingly, there remains room for improvement in the field of archery bows, and in particular, axle systems for rotating cams.